Advanced Marine Engineering interview questions

125 questions with answers (MAR-301 to MAR-425). Try each one aloud before reading the answer.

Ship Construction & Naval Architecture

MAR-301 · A hull girder has a bending moment of 800 MN·m and a midship section modulus of 20 m³. What is the bending stress?

σ = M/Z = 800 × 10⁶ N·m / 20 m³ = 40 × 10⁶ Pa = 40 MPa. This is compared with the class allowable stress for the steel grade used.

MAR-302 · A ship has L = 200 m, B = 32 m, T = 12 m and a displacement of 60,000 t in seawater. Find Cb.

∇ = 60,000 / 1.025 = 58,537 m³. Cb = ∇/(L·B·T) = 58,537 / 76,800 ≈ 0.76, typical of a bulk carrier or tanker.

MAR-303 · What are the trade-offs of using high-tensile steel in hull construction?

It allows thinner, lighter scantlings and more cargo capacity. But thinner plating is more prone to buckling, fatigue cracking and loss of strength from corrosion, so detail design and coating become more critical.

MAR-304 · Why do container ships need special torsional strength design?

Wide hatch openings remove most deck plating, making the hull an open section with low torsional stiffness. Designers add torsion boxes, thick sheer strakes and heavy hatch coamings to resist twisting in oblique seas.

MAR-305 · Why are hatch corners rounded or elliptical?

Sharp corners concentrate stress and start fatigue cracks. Rounded or elliptical corners with thicker insert plates of higher-grade steel spread the stress.

MAR-306 · Compare impressed current cathodic protection (ICCP) with sacrificial anodes.

Sacrificial zinc or aluminium anodes corrode instead of the hull and need no power, but must be renewed. ICCP uses inert anodes with a controlled DC current, adjusts to conditions and suits large hulls, but needs power and monitoring and can over-protect and damage paint.

MAR-307 · What is the probabilistic damage stability approach in SOLAS?

The attained subdivision index A, summing the probability of each damage case times the probability of survival, must be at least the required index R. It replaced deterministic compartment standards for cargo and passenger ships.

MAR-308 · What are the IACS Common Structural Rules?

Harmonised rules for the structural design of oil tankers and bulk carriers adopted by all IACS members. They use net scantlings plus corrosion additions and include fatigue and ultimate strength checks.

MAR-309 · How is brittle fracture prevented in ship steel?

By using steel grades with tested Charpy impact toughness at low temperatures, especially in highly stressed areas such as the sheer strake and bilge strake, and by avoiding notches and poor welds.

MAR-310 · A crack is found in the main deck plating at sea. What do you do?

Assess its length and location, drill crack-arrest holes at its tips, reduce hull stresses by adjusting ballast, speed and heading, monitor it, inform the company and class, and arrange a permanent repair approved by class.

MAR-311 · Why are long tankers longitudinally framed but their transverse webs still needed?

Longitudinals resist hull girder bending and plate buckling efficiently. Widely spaced web frames and transverse bulkheads still support the longitudinals and provide transverse strength against water and cargo pressure.

Ship Stability

MAR-312 · What is the free surface effect, and calculate it for a 12 m × 10 m tank of oil (ρ = 0.9 t/m³) on a 15,000 t ship.

Liquid in a slack tank moves to the low side, which acts as a rise in G and reduces GM. i = l·b³/12 = 12 × 10³/12 = 1000 m⁴. Virtual rise GG′ = i·ρ/Δ = 1000 × 0.9 / 15,000 = 0.06 m.

MAR-313 · How does subdividing a tank longitudinally reduce the free surface effect?

FSE depends on b³. Dividing a tank into n equal longitudinal compartments reduces the total effect to 1/n² of the original, so one centreline division cuts it to one quarter.

MAR-314 · A ship has KB = 4.0 m, BM = 5.0 m, KG = 8.2 m and a free surface correction of 0.1 m. Find the fluid GM.

KM = KB + BM = 9.0 m. Solid GM = 9.0 − 8.2 = 0.8 m. Fluid GM = 0.8 − 0.1 = 0.7 m.

MAR-315 · In an inclining test, 20 t is moved 10 m across a 8,000 t ship and a 6 m pendulum deflects 0.15 m. Find GM.

tanθ = 0.15/6 = 0.025. GM = w·d/(Δ·tanθ) = 20 × 10 / (8,000 × 0.025) = 1.0 m.

MAR-316 · A 50 t weight is loaded 8 m off the centreline, giving a final displacement of 10,000 t and GM of 1.2 m. Find the list.

tanθ = w·d/(Δ·GM) = 50 × 8 / (10,000 × 1.2) = 0.0333, so θ ≈ 1.9° towards the side of the weight.

MAR-317 · 200 t is loaded 40 m forward of the LCF (at amidships). MCTC = 250 t·m/cm and TPC = 30. Find the new draft changes.

Trim change = 200 × 40 / 250 = 32 cm by the head. Sinkage = 200/30 = 6.7 cm. With LCF amidships, forward draft rises by 16 + 6.7 = 22.7 cm and aft draft changes by −16 + 6.7 = −9.3 cm.

MAR-318 · What are the main IMO intact stability criteria for cargo ships?

Under the 2008 IS Code: area under GZ to 30° ≥ 0.055 m·rad, to 40° (or flooding angle) ≥ 0.09 m·rad, between 30° and 40° ≥ 0.03 m·rad; GZ ≥ 0.20 m at 30° or more; maximum GZ at 25° or more; and initial GM ≥ 0.15 m.

MAR-319 · A ship develops an angle of loll. How do you correct it?

Confirm it is loll (negative GM) not list. Lower G by removing high weights or ballasting low tanks, starting with the smallest divided double-bottom tank on the low side to limit free surface. Never shift weights across to the high side, which can cause a sudden roll to a larger angle.

MAR-320 · Why are bulk grain cargoes a special stability hazard?

Grain settles and shifts in heavy weather, creating a heeling moment and free surface. The International Grain Code requires stability to be checked for assumed grain shifts, with the heel angle limited to 12°.

MAR-321 · How is flooding treated in damage stability calculations?

By the lost buoyancy method, where the flooded space is removed from buoyancy and displacement stays constant, or the added weight method. Permeability, the fraction of a space water can occupy, is applied, for example 0.85 for machinery spaces.

MAR-322 · What is parametric rolling and how is it avoided?

Large roll from periodic changes in waterplane, and so GM, as waves pass. It is worst when the encounter period is about half the natural roll period, in head or following seas, especially on container ships. Avoid by changing speed and heading.

Resistance & Propulsion

MAR-323 · What are the components of ship resistance?

Frictional resistance, which depends on Reynolds number and wetted surface, and residuary resistance, mainly wave-making, which depends on Froude number. Viscous pressure (form), appendage and air resistance are smaller parts.

MAR-324 · Calculate the ITTC 1957 friction coefficient for a 200 m ship at 8 m/s (ν = 1.19 × 10⁻⁶ m²/s).

Rn = VL/ν = 8 × 200 / 1.19 × 10⁻⁶ ≈ 1.34 × 10⁹. log₁₀Rn ≈ 9.13. Cf = 0.075/(9.13 − 2)² = 0.075/50.8 ≈ 0.00148.

MAR-325 · A propeller has 5 m pitch and runs at 100 rpm while the ship makes 14 knots. Find apparent slip.

Theoretical speed = 5 × 100 × 60 = 30,000 m/h = 16.2 knots. Slip = (16.2 − 14)/16.2 ≈ 13.6%.

MAR-326 · A ship needs 10,000 kW at 15 knots. Estimate power at 13 knots and the fuel saved per voyage.

Using P ∝ V³, P = 10,000 × (13/15)³ ≈ 6,510 kW. Fuel per voyage scales with V², so it falls to (13/15)² ≈ 75%, a saving of about 25%, though the voyage takes longer.

MAR-327 · What is the light running margin in propeller design?

The propeller is designed slightly "light", turning a few percent faster than the engine's nominal curve at trial. As hull fouling and weather add resistance, the propeller becomes heavier, and the margin keeps the engine from being overloaded at rated rpm.

MAR-328 · A ship has V = 15 kn, Va = 12 kn and thrust deduction t = 0.17. Find hull efficiency.

w = (15 − 12)/15 = 0.20. ηH = (1 − t)/(1 − w) = 0.83/0.80 ≈ 1.04.

MAR-329 · Compare CPP and FPP for a ship design.

CPP gives fast thrust reversal, constant-speed operation for shaft generators and good manoeuvring, but costs more, is more complex and has a larger hub with slightly lower efficiency at design point. FPP is simple, robust and efficient at design, but needs a reversible engine or gearbox.

MAR-330 · How are model test results scaled to full size?

Froude's method: test at the same Froude number, split resistance into frictional (from a friction line at model Rn) and residuary. The residuary coefficient is the same for model and ship, and ship friction is then added at full-scale Rn, often with a form factor (1 + k).

MAR-331 · How do designers reduce propeller cavitation?

Increase blade area ratio, use skew, lower the rpm with a larger diameter, improve wake uniformity, and keep the propeller deeply immersed. The cavitation number σ = (p₀ − pv)/(½ρV²) is checked against design charts.

MAR-332 · What energy-saving devices improve propulsion efficiency?

Pre-swirl ducts and stators, propeller boss cap fins, rudder bulbs, high-efficiency rudders, air lubrication systems and low-friction hull coatings. Each targets wake, rotational or frictional losses.

MAR-333 · What is a barred speed range?

An rpm range where the shaft system's torsional vibration stresses exceed limits. The engine must pass through it quickly and must not run continuously in it.

Marine Diesel Engines

MAR-334 · Why are two-stroke slow-speed engines used on large ships?

They couple directly to a large, efficient slow-turning propeller without a gearbox, reach thermal efficiency near 50%, burn heavy fuel reliably, and are simple to reverse. Long stroke and crosshead design suit low rpm and high power per cylinder.

MAR-335 · Find the indicated power of a 6-cylinder two-stroke engine with bore 0.6 m, stroke 2.4 m, pmi 20 bar and 100 rpm.

A = π × 0.6²/4 = 0.283 m². Per cylinder: 20 × 10⁵ × 2.4 × 0.283 × (100/60) ≈ 2.26 MW. Total IP ≈ 6 × 2.26 ≈ 13.6 MW.

MAR-336 · An engine has SFOC of 170 g/kWh on fuel with LCV 42,700 kJ/kg. Find its brake thermal efficiency.

η = 3600 / (SFOC × LCV) = 3600 / (0.170 × 42,700) = 3600 / 7,259 ≈ 49.6%.

MAR-337 · Calculate the mean piston speed of an engine with 2.4 m stroke at 100 rpm.

cm = 2 × S × N/60 = 2 × 2.4 × 100/60 = 8 m/s. Mean piston speed limits ring and liner wear and inertia loads.

MAR-338 · One cylinder shows a high exhaust temperature. How do you diagnose it?

Compare the cylinder's pressures and temperatures with the others. Likely causes are a defective injector (poor atomisation or dribbling), a leaking exhaust valve, blow-by past rings, late injection or a faulty thermocouple. Take indicator or pressure readings and check the injector first.

MAR-339 · The oil mist detector alarms on the main engine. What do you do?

Inform the bridge and reduce speed or stop as per the manufacturer's guidance. Keep people away from crankcase doors and relief valves. Keep lube oil circulating, and do not open the crankcase until it has cooled for the time required. Then find and fix the hot spot before restarting.

MAR-340 · What problems does prolonged slow steaming cause on two-stroke engines?

Poor combustion and fouling of turbochargers and exhaust boilers, low exhaust temperatures, risk of cold corrosion from low liner temperatures, and auxiliary blowers running more. Remedies include turbocharger cut-out, cylinder oil feed adjustment and engine tuning for part load.

MAR-341 · Compare SCR and EGR for meeting IMO Tier III NOx.

SCR injects urea into the exhaust over a catalyst, cutting NOx by up to about 90% without hurting engine efficiency, but needs urea and enough exhaust temperature. EGR recirculates cooled exhaust to lower combustion temperature, needs no reagent, but needs scrubbing of recirculated gas and slightly raises fuel use.

MAR-342 · Compare high-pressure and low-pressure dual-fuel two-stroke engines.

High-pressure (diesel cycle) engines inject gas at high pressure after compression, giving low methane slip and no knocking but needing high-pressure gas compressors. Low-pressure (Otto cycle) engines admit gas during compression, meet Tier III without after-treatment but have higher methane slip and knock risk.

MAR-343 · The main engine fails to start on air. What are the likely causes?

Low starting air pressure, closed main air valve, turning gear engaged, faulty starting air distributor or valves, control air failure, an interlock (such as low lube oil pressure), or crank stopped at a dead position.

MAR-344 · Why is cylinder oil feed rate tied to fuel sulphur and liner condition?

Feed must supply enough base to neutralise acids from fuel sulphur and keep a lubricating film. Modern systems use a feed rate proportional to load and sulphur content, adjusted by scrape-down oil analysis for iron and residual BN.

Marine Boilers & Steam Systems

MAR-345 · A boiler makes 2,000 kg/h of steam (h = 2,770 kJ/kg) from feed at 80 °C (h = 335 kJ/kg) burning 150 kg/h of fuel with LCV 40,000 kJ/kg. Find efficiency.

Heat to steam = 2,000 × (2,770 − 335) = 4.87 × 10⁶ kJ/h. Heat input = 150 × 40,000 = 6.0 × 10⁶ kJ/h. η ≈ 4.87/6.0 ≈ 81%.

MAR-346 · The water level has fallen out of sight in the gauge glass. What do you do?

Shut off the burner immediately and do not add feed water, because cold water on overheated surfaces can cause tube failure or explosion. Close the main steam stop, let the boiler cool, then inspect for damage before refilling.

MAR-347 · How does a soot fire turn into a hydrogen or iron fire, and what is the response?

If a soot fire raises tube temperatures far enough, water or steam dissociates into hydrogen and oxygen, and the steel itself can burn. Stop the main engine, do not use steam soot blowers, keep water circulating if possible, and use large quantities of water for cooling, because small amounts feed the fire.

MAR-348 · What is caustic embrittlement?

Intergranular cracking of boiler steel at stressed areas such as rivets or tube ends, where concentrated sodium hydroxide accumulates. It is prevented by controlling free alkalinity and avoiding crevices.

MAR-349 · How are boiler safety valves set?

Each valve is set separately with the others gagged, by raising pressure until it lifts at the set point, normally witnessed by a class surveyor. Gags are removed afterward, and an accumulation test may follow.

MAR-350 · Why must exhaust gas boiler outlet temperature stay above a limit?

Below the sulphuric acid dew point, acid condenses on cold surfaces and causes corrosion and soot sticking. The design balances heat recovery against this low-temperature limit.

MAR-351 · How is combustion optimised in an oil-fired boiler?

By keeping the right air-fuel ratio with minimum excess air, monitored by flue gas O₂ or CO₂ and smoke. Too little air gives smoke and soot; too much lowers efficiency through heat lost in flue gas.

MAR-352 · Oil is seen in the hotwell. What do you do?

Isolate the drains from heating coils one by one to find the leaking coil, skim and drain the oil, and divert contaminated condensate. Check boiler water for oil, and do not let oily water reach the boiler, as it causes foaming and overheating of tubes.

MAR-353 · What causes a furnace explosion or blow-back and how is it prevented?

Unburnt fuel vapour accumulates and ignites suddenly, often after a failed ignition or a leaking fuel valve. Prevention is a proper pre-purge, a working flame scanner, tight fuel valves and limiting ignition attempts.

MAR-354 · Why did LNG carriers move from steam turbines to dual-fuel diesel plants?

Steam turbines easily burn boil-off gas but have low thermal efficiency, around 30%. Dual-fuel diesel and two-stroke gas engines offer much higher efficiency and lower fuel use, while reliquefaction or engines still use the boil-off.

MAR-355 · Why is phosphate treatment used in boiler water?

Phosphate precipitates calcium and magnesium as soft sludge instead of hard scale, and it buffers pH against caustic attack. The sludge is removed by bottom blowdown.

Auxiliary Machinery (Pumps, Purifiers, Compressors, FWG)

MAR-356 · Find the power for a seawater pump delivering 0.1 m³/s against 30 m head with 70% efficiency.

P = ρgQH/η = 1,025 × 9.81 × 0.1 × 30 / 0.7 ≈ 43 kW.

MAR-357 · If a centrifugal pump's speed is cut by 10%, what happens to flow, head and power?

By the affinity laws: Q ∝ N, H ∝ N², P ∝ N³. Flow drops to 90%, head to 81% and power to about 73%, which is why variable-speed drives save energy.

MAR-358 · How is the starting air receiver capacity specified?

Class rules require enough air, without refilling, for at least 12 consecutive starts of each reversible main engine (alternating ahead and astern) or 6 starts of a non-reversible engine.

MAR-359 · The FWG output drops. What could be the causes?

Low jacket water temperature or flow, poor vacuum from air leaks or a faulty ejector, scaled evaporator plates, fouled condenser, wrong feed rate, or a blocked distillate pump.

MAR-360 · The FWG salinity alarm sounds. What do you check?

Check for priming from high brine level or too high vacuum, a damaged demister, leaking condenser plates or tubes, or brine pump failure. The distillate is dumped automatically until salinity is back within the limit.

MAR-361 · Estimate FWG output if jacket water is 80 t/h cooled by 10 K.

Q = ṁ·cp·ΔT = (80,000/3,600) × 4.18 × 10 ≈ 929 kW. With latent heat ≈ 2,400 kJ/kg, output ≈ 0.39 kg/s ≈ 33 t/day.

MAR-362 · Compare plate and shell-and-tube heat exchangers for seawater cooling.

Plate exchangers are compact, highly efficient and easy to expand, but gaskets limit temperature and pressure, and they foul with narrow gaps. Shell-and-tube units handle higher pressures and dirtier fluids and tolerate fouling better, but are larger and heavier.

MAR-363 · How do you choose a ballast water treatment system?

Consider ballast flow rate, water salinity and turbidity on the trade route, power demand, footprint, hazardous-area needs for tankers, and holding time. UV systems struggle in turbid water; electrochlorination needs enough salinity and control of total residual oxidant at discharge.

MAR-364 · Why is tampering with the OWS or using a bypass ("magic pipe") so serious?

It discharges oily water illegally and falsifies the Oil Record Book. It leads to heavy fines, ship detention and criminal prosecution of the crew and company.

MAR-365 · What steering gear tests are required before departure?

Within 12 hours before departure, SOLAS requires checking and testing the gear, including full movement, power units, remote control systems, emergency power, rudder angle indicators and alarms. Emergency steering drills are held at least every three months.

Marine Electrical Systems

MAR-366 · How do you size the generators for a cargo ship?

Do an electrical load analysis for each condition (sea, manoeuvring, port, emergency) using demand and diversity factors. Pick sets so the largest load case is covered with one generator out of service, and generators run at an efficient 70–85% load.

MAR-367 · Find the full-load current of an 800 kW, 440 V, 0.8 power factor generator.

S = P/pf = 800/0.8 = 1,000 kVA. I = S/(√3·V) = 1,000,000/(1.732 × 440) ≈ 1,312 A.

MAR-368 · Find the current drawn by a 50 kW, 440 V motor with pf 0.85 and efficiency 90%.

Input = 50/0.9 = 55.6 kW. I = P/(√3·V·pf) = 55,600/(1.732 × 440 × 0.85) ≈ 86 A.

MAR-369 · Why are high-voltage ship systems often high-resistance earthed rather than insulated?

A resistor limits earth fault current to a low value, preventing dangerous transient overvoltages that can occur with an insulated HV neutral, while still allowing the fault to be detected and selectively tripped.

MAR-370 · What is protection discrimination?

Setting breakers and fuses so that only the device closest to a fault trips, leaving the rest of the system supplied. It uses time-current grading between generator, feeder and consumer breakers.

MAR-371 · What are the pros and cons of diesel-electric propulsion?

Pros: generators run at optimum load, flexible layout, good redundancy, quiet operation and fine manoeuvring control, suiting cruise ships and offshore vessels. Cons: conversion losses of several percent, higher cost and complex power electronics.

MAR-372 · Why are harmonics a concern with variable frequency drives?

VFDs draw non-sinusoidal current, distorting busbar voltage. This heats generators and motors, upsets sensitive electronics and protection, so harmonic filters, multi-pulse rectifiers or active front ends are used.

MAR-373 · A generator trips on reverse power while you transfer load. Why, and what next?

The outgoing set's load was reduced too far, or its governor or fuel failed, so it motored. Check the remaining set is not overloaded, check the tripped engine's fuel and governor, and when transferring, unload gradually and open the breaker at low positive load.

MAR-374 · What electrical equipment is permitted in hazardous areas on tankers?

Only certified explosion-protected equipment suited to the zone and gas group, such as flameproof (Ex d), increased safety (Ex e), intrinsically safe (Ex i) or pressurised (Ex p).

MAR-375 · A blackout occurs while manoeuvring in a channel. What actions follow?

Inform the bridge so they can anchor or call tugs. Make sure the emergency generator has supplied steering and lights. Restart a main generator, often by auto-standby, then restart lube, cooling and fuel pumps in order and reset the main engine for starting.

Refrigeration & AC on Ships

MAR-376 · A plant removes 50 kW of heat using 15 kW of power. Compare its COP to the Carnot COP between −25 °C and +35 °C.

Actual COP = 50/15 ≈ 3.3. Carnot COP = Te/(Tc − Te) = 248/(308 − 248) ≈ 4.1. The actual plant reaches about 80% of the ideal.

MAR-377 · Given evaporator outlet h₁ = 395 kJ/kg, compressor outlet h₂ = 430 kJ/kg and condenser outlet h₃ = 250 kJ/kg, find COP and mass flow for 30 kW.

Refrigerating effect = 395 − 250 = 145 kJ/kg. Work = 430 − 395 = 35 kJ/kg. COP = 145/35 ≈ 4.1. Mass flow = 30/145 ≈ 0.21 kg/s.

MAR-378 · How would you choose a refrigerant for a new ship's provision plant?

Balance zero ozone depletion, low GWP for future regulation, safety (toxicity, flammability), operating pressures and efficiency. CO₂ is safe and low-GWP but needs very high pressures; ammonia is efficient but toxic; HFC blends are easy but face phase-down.

MAR-379 · The compressor short-cycles. What are the likely causes?

Low refrigerant charge tripping the LP cut-out, thermostat differential set too small, a leaking solenoid valve, iced evaporator, or HP cut-out from condenser cooling failure.

MAR-380 · The freezer room temperature is rising. How do you troubleshoot?

Check evaporator icing and defrost, fan operation, door seals, solenoid and expansion valves, charge (sight glass), suction and discharge pressures, and condenser cooling water.

MAR-381 · Why is two-stage compression used for very low temperatures?

A single stage across a large pressure ratio gives high discharge temperature and poor volumetric efficiency. Two stages with intercooling lower discharge temperature and power.

MAR-382 · What is the difference between flooded and direct expansion (DX) evaporators?

DX evaporators feed just enough liquid through an expansion valve to fully evaporate, giving superheated outlet vapour. Flooded evaporators keep the coil full of liquid with a separator, giving better heat transfer but needing a larger charge.

MAR-383 · What are the legal requirements when handling refrigerant leaks?

Deliberate venting of ozone-depleting substances is banned under MARPOL Annex VI. Ships with rechargeable ODS systems keep an ODS record book, and refrigerant must be recovered into approved cylinders.

MAR-384 · How is the air conditioning cooling load estimated?

Add sensible heat (solar gain, conduction, people, lighting, equipment) and latent heat (moisture from people and outside air). A psychrometric chart sets supply air conditions and coil capacity.

MAR-385 · How does controlled atmosphere help reefer cargo?

Lowering oxygen and controlling CO₂ slows ripening and respiration of fruit, extending storage life beyond what temperature control alone can achieve.

Fuels, Lubrication & Bunkering

MAR-386 · What is IMO 2020?

A global MARPOL Annex VI cap of 0.50% m/m sulphur in marine fuel from 1 January 2020, down from 3.50%. Ships comply with VLSFO, distillates, LNG, or an approved exhaust gas scrubber while burning high-sulphur fuel.

MAR-387 · What operational problems come with VLSFO?

Variable stability and compatibility between batches, sludge, cat fines, wide viscosity range, variable ignition quality and wax at low temperatures. Compatibility tests and segregation are needed.

MAR-388 · Compare open-loop and closed-loop scrubbers.

Open-loop scrubbers use seawater alkalinity and discharge washwater overboard, which is simple but banned in some ports. Closed-loop units recirculate washwater dosed with caustic soda, discharge little, but need chemicals and more equipment.

MAR-389 · 500 m³ of HFO is loaded at 50 °C with a VCF of 0.977 and density at 15 °C of 0.990 t/m³. Find the mass.

V₁₅ = 500 × 0.977 = 488.5 m³. Mass = 488.5 × 0.990 ≈ 484 t.

MAR-390 · Find the daily fuel consumption of a 12,000 kW engine at 175 g/kWh.

12,000 × 0.175 kg/kWh × 24 h = 50,400 kg ≈ 50.4 t/day.

MAR-391 · Bunker analysis shows the fuel is off-spec. What do you do?

Avoid using the fuel where possible, issue a letter of protest, inform the company and supplier, keep sealed samples for independent testing, and plan debunkering or special handling as agreed.

MAR-392 · Fuel contains 50 mg/kg of Al + Si and the engine maker recommends 15 mg/kg at the engine inlet. What removal efficiency is needed?

Required efficiency = (50 − 15)/50 = 70%. Achieve it by slow purifier throughput, optimal temperature, series operation, settling and draining tanks.

MAR-393 · Lube oil analysis shows rising viscosity, falling TBN and high water. What do these mean?

Rising viscosity suggests oxidation or HFO contamination; falling BN shows depleted additives or acid build-up; water points to cooler leaks or condensation. Find and fix the source, purify and partly renew the charge.

MAR-394 · What are the safety issues of LNG as a marine fuel?

Cryogenic temperatures can embrittle steel, methane is flammable and asphyxiating, and boil-off must be managed. The IGF Code requires gas-safe machinery spaces, double-walled pipes, ventilation and gas detection.

MAR-395 · Why is water in lube oil dangerous and how is it handled?

It breaks the oil film, causes corrosion and bearing damage, and can form emulsions and microbial growth. Locate the leak (cooler, jacket water, condensation), purify continuously and renew oil if it cannot be cleaned.

Maritime Regulations (SOLAS, MARPOL, STCW, ISM, ISPS)

MAR-396 · What do MARPOL and SOLAS cover?

MARPOL covers prevention of pollution from ships (oil, chemicals, packaged goods, sewage, garbage, air emissions). SOLAS covers safety of life at sea (construction, fire safety, life-saving, radio, navigation, ISM and ISPS).

MAR-397 · What are EEXI and CII?

EEXI is a one-time technical index of design energy efficiency for existing ships, often met by engine or shaft power limitation. CII is an annual operational carbon intensity rating (A–E) of grams of CO₂ per tonne-mile; ships rated D for three years or E need a corrective plan.

MAR-398 · A ship of 50,000 DWT burns 10,000 t HFO and sails 70,000 nm in a year. Find its CII (Cf = 3.114).

CO₂ = 10,000 × 3.114 = 31,140 t. CII = 31,140 × 10⁶ g / (50,000 × 70,000) ≈ 8.9 g CO₂/(t·nm).

MAR-399 · What are the D-1 and D-2 ballast water standards?

D-1 is ballast exchange of at least 95% volume, normally at least 200 nm from land in water at least 200 m deep. D-2 is a discharge standard, such as fewer than 10 viable organisms per m³ of 50 µm or more, met by treatment systems.

MAR-400 · What are MARPOL limits for oily water discharge from a tanker's cargo area?

The tanker must be more than 50 nm from land, en route, outside special areas, with instantaneous discharge rate not above 30 litres per nautical mile, total not above 1/30,000 of the last cargo (for newer tankers), and an ODME operating.

MAR-401 · What are the MARPOL Annex IV sewage discharge rules?

Comminuted and disinfected sewage may be discharged more than 3 nm from land; untreated sewage more than 12 nm from land at a moderate rate while sailing at no less than 4 knots; or treated sewage from an approved plant, with stricter rules for passenger ships in special areas.

MAR-402 · What are the STCW engineering certificates of competency?

Regulation III/1 for officer in charge of an engineering watch (750 kW and above), III/2 for chief and second engineers on ships of 3,000 kW or more, and III/3 for chief and second engineers on ships of 750–3,000 kW.

MAR-403 · How is a major ISM non-conformity handled?

It is a serious deviation threatening safety or the environment, or a systemic failure. It must be corrected immediately or downgraded with corrective action before the ship sails, followed by root cause analysis and verification.

MAR-404 · A port state control officer finds detainable deficiencies. What happens?

The ship is detained until the deficiencies are fixed and verified, the flag and class are notified, and the detention is published. Repeated detentions increase inspection frequency and may lead to banning.

MAR-405 · What is the Ship Security Alert System (SSAS)?

A covert alert that, when activated, sends a security alert to the company and flag without alarming anyone on board. It is required by SOLAS XI-2 and is part of the ISPS framework.

Safety, Firefighting & Survival

MAR-406 · Estimate the CO₂ needed for an engine room of 5,000 m³ gross volume (excluding casing).

The FSS Code requires 40% of gross volume excluding casing (or 35% including casing, whichever is more), with free gas volume 0.56 m³/kg. 0.40 × 5,000 = 2,000 m³ → 2,000/0.56 ≈ 3,570 kg, about 80 cylinders of 45 kg.

MAR-407 · A fire breaks out in the engine room. What are the actions?

Raise the alarm, inform the bridge, attempt to fight it with portable means if safe, and isolate fuel with quick-closing valves and remote stops. Close ventilation, muster and account for personnel, start boundary cooling, and if it is not controlled, evacuate and release the fixed system.

MAR-408 · Why is local water mist protection fitted over purifiers and generators?

These are high fire-risk areas where fuel can spray onto hot surfaces. A local application water-based system can suppress a fire quickly without evacuating the whole engine room or flooding it with CO₂.

MAR-409 · What are A-60, A-0 and B-class divisions?

A-class divisions are steel bulkheads or decks that stop smoke and flame for 60 minutes in the standard fire test. The number gives the insulation rating in minutes that keeps the unexposed side's average temperature rise within 140 °C. B-class divisions resist flame for 30 minutes.

MAR-410 · A crew member collapses inside an enclosed space. What do you do?

Raise the alarm and do not enter without breathing apparatus. The rescue team enters with SCBA and lifelines, ventilates the space, gives oxygen and evacuates the casualty with a rescue stretcher or tripod.

MAR-411 · Why have lifeboat on-load release hooks caused accidents?

Poor design, wear or wrong resetting led to hooks opening early and dropping boats during drills. SOLAS now requires hooks to meet stricter LSA Code standards, with fall preventer devices and careful maintenance.

MAR-412 · What precautions are taken for hot work in the engine room?

A permit to work, risk assessment, gas-free tests, removal or covering of combustibles, checking adjacent tanks and spaces, a fire watch with extinguishers, and a check of the area after work.

MAR-413 · The engine room starts flooding. What are the actions?

Raise the alarm, inform the bridge, find and isolate the source, and start bilge pumps. If needed, use the emergency bilge suction connected to the largest seawater pump. Protect electrical equipment and prepare for loss of power.

MAR-414 · How are fire detectors chosen for different spaces?

Smoke detectors suit accommodation; heat detectors suit galleys and spaces with normal smoke or steam; flame detectors suit engine rooms with flammable liquids where fires grow fast.

MAR-415 · What decides whether to abandon ship?

The Master decides, when the ship is about to sink or when fire or flooding cannot be controlled and staying is more dangerous. Crew muster, don lifejackets and immersion suits, launch survival craft and activate EPIRB and SART.

Engine Room Operations & Watchkeeping

MAR-416 · How do you use performance monitoring to plan maintenance?

Compare readings such as exhaust temperatures, scavenge pressure, air cooler pressure drop and turbocharger rpm with shop trial curves at the same load. Deviations show fouling, wear or injector faults, and maintenance is planned by condition.

MAR-417 · A blackout occurs at sea in heavy weather near the coast. What do you prioritise?

Restore power fast to steering and propulsion auxiliaries, keep the bridge informed so anchors can be prepared, and confirm emergency power to steering and navigation lights. Restart the main engine as soon as safely possible.

MAR-418 · What is the difference between a main engine slowdown and a shutdown?

A slowdown reduces load automatically for faults that are not immediately damaging, such as high temperature. A shutdown stops the engine for critical faults like very low lube oil pressure or overspeed. The bridge may override some slowdowns for ship safety.

MAR-419 · The main engine jacket water outlet temperature rises. How do you investigate?

Check the cooler and its seawater side, the three-way valve controller, pump pressure, expansion tank level, and for air or combustion gas in the system. Isolated high readings on one cylinder may mean a cracked liner or cover.

MAR-420 · A fuel tank overflows during bunkering. What do you do?

Stop bunkering immediately, contain oil on deck using SOPEP equipment, close relevant valves, inform the Master, the terminal and authorities as required, start clean-up and record the event.

MAR-421 · How do you plan an engine room dry-dock job list?

Use PMS, class survey due dates, condition monitoring and defect reports to list jobs such as sea chest valves, stern tube seals, propeller polishing, anodes and overboard valves. Agree specifications, spares and isolation plans with the yard before arrival.

MAR-422 · How is a crankcase inspection carried out on a main engine?

After stopping and cooling, isolate the starting air, engage the turning gear, ventilate the crankcase and check atmosphere. Inspect bearings, crossheads and white metal flakes, check bolts and locking devices, and look for water or debris.

MAR-423 · A seawater pipe bursts near the sea chest. What do you do?

Inform the bridge, stop the pump, close the sea chest valve if reachable, and change to the other sea chest. Contain the flooding with bilge pumps and apply a temporary clamp or patch until a proper repair.

MAR-424 · You are the duty engineer on UMS and an alarm sounds at night. What do you do?

Inform the bridge you are attending, go to the engine room (with a second person if required), acknowledge and investigate the alarm, rectify it or call the Chief Engineer if needed, and log the event.

MAR-425 · How can engine room electrical load be reduced to save fuel?

Use variable speed drives on pumps and fans, run the minimum number of generators at efficient load, use shaft generators at sea, optimise HVAC, and switch off unnecessary heaters and lighting.

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